Deaeration of paper making fibers



Oct. 16, 1951 J. A. DE cEw 2,571,219

DEAERATION OF PAPER MAKING FIBERS Original Filed April 2'7, 1946 2Sheets-Sheet l ll mmllm INVENTOR: Judson A. De Cew BY WMM ATTORNEY Oct.16, 1951 I J. A. DE CEW 2,571,219

DEAERATION OF PAPER MAKING FIBERS Original Filed April 27, 1,946 2Sheets-Sheet 2 gm'g HEAD BOX OF PAPER MACHINE INVENTOR: Judson A. De CewATTORNEY Patented Oct. 16, 1951 UNITED STATES PATENT OFFICE Continuationof application Serial No. 665,408, April 2'7, 1946. This application May17, 1950,

Serial No. 162,542

5 Claims.

This invention relates to the treatment of conditioning of paper-makingstock as it is diluted or rendered into a suspension to be ready for thepaper-making machine. With the ever-increasing demand for more and morespeed and capacity for paper-making machines, it is necessary to removehuge quantities of Water from the stock while on the paper machine, soone of the objects of this invention is to facilitate that removal.Frothing of the paper stock as it goes onto the paper machine is anotherproblem, so another object of this invention is to minimize such frothformation. Another problem is to minimize flocculation of the fibers ofthe paper stock since that tends to slow down the rate of water removal.So it is still further an object of this invention to prevent or atleast-deter such flocculation. I have found that a significant cause ofthese troubles is the presence not only of entrained air or gas in thepaper stock, but more particularly the presence of air or gas that isdissolved in the water carrying such stock. So an important object ofthis invention is the removal of such air or gas from the stock at apoint just ahead of the paper-making machine.

In normal paper-making operations, the diluted paper stock is pumped,under pressure, to the screens or head-box and while under suchpressure, a part of the entrained air becomes dissolved. When thispressure is released to atmospheric pressure, a large portion of thedissolved air comes out of solution and in changing phase, forms into amyriad of microscopic bubbles. These bubbles form on and adhere to thefibers of the paper-stock and, in addition, air or gas is adsorbed bythe surfaces of the fibers. This seems to cause the fibers to beattracted to each other, apparently due to static electricity, so thatthe fibers form into fiocs. As a result both of this adhesion of bubblesand this flocculation, the fibers, if given the opportunity, will floatto the surface and form a frothy mass of fibers. Fiber flocculation is awell recognized phenomenon that always takes place in ordinarypaper-making operations and is the cause of the non-uniform orheterogeneous concentration of the fibers in many papers. This conditionshows itself when a piece of such paper is held between the viewer andthe light, whereupon the irregular concentrations of fibers appear asclouds. If attempt is made by ordinary means to remove substantially allair from the stock, it has been found that such air or gas in itsvarious phases is removed in the following order: first, free orentrained air or gas will escape quickly; second;

(c1. lea-2.5)

dissolved air or gas will begin to come out of solution and that whichdoes not become attached to the fibers will escape slowly; and third,the air or gas adsorbed or attached to the fibers is very slowlyremoved. In commercial operations in paper making, there is no time forthe removal of such air or gas in these three stages or steps.

All of these disadvantages can be palliated, if not obviated, by thepractice of this invention. The invention revolves about the method andmeans embodied in a suitably supported closed tank having anunobstructed interior, and which is subjected to suction. The tank has abody portion with a depending leg portion. Stock is pumped to the uppersection of the body portion of the tank and released thereinto by meansof a specially constructed spray or atomizing nozzle or nozzles; Thestock so released in the form of a very fine spray encounters thevacuum-induced suction in the tank, whereupon air or gas of the stock,both entrained and dissolved, is sucked out of the droplets and fibersof the stock and from the tank through the vacuum pump (or othersuction-producing means) to the atmosphere. The de-aerated fibers sinkin the tank and fall down into the depending leg, dispersed in thewater. The tank is completely smooth inside for such de-aerated stock,or succession of fibers, are actively adherent to anything in the tanktowhich they may cling. Therefore, there should be a minimum ofobstructions, bafiles, contact shelves, or other such surfaces in thetank so that this clinging tendency will not have a chance to exertitself. The conditioned and de-aerated fibers in suspension areconducted from the leg to the cylinder-mold vat or to the head box ofthe paper-making machine, either by gravity or by pump.

Certain features of this embodiment must meet specific requirements. Forinstance, it takes time for the air to get out. So with the enormousvolumes of stock to be treated, it is imperative to cut down theduration of this time interval. In so doing, it is important to takeinto consideration the following factors: the amount of air to beremoved; the size of the tank for the larger the tank the more spraynozzles can be used and the less can be the vacuum used; and thefineness of the spray which is the result of the pressure with which thestock is forced through the emission orifice of each nozzle. The spraynozzle must be of a type that contains no obstructions, ribs, spokes,vanes, or the like, on

which fibers can lodge, adhere or collect for they 3 would quickly clogup the nozzle. In other words, the nozzle has an unobstructedflow-passage therethrough. There must be a constant supply of feed stockpassing into the tank for treatment therein, and the treated stock mustbe removed from the tank at such an assured rate that there issubstantially no stock detained in the tank. That is, the treated stockwhich is in fluid form and presents a liquid level, must be so transitedthat as far as possible no liquid level thereof is developed in thetank. To that end, the depending leg is provided for the tank to hold anaccumulated body of treated stock so that the variation of its liquidlevel ranges Within the leg. The reason for not wanting the liquid levelwithin the vacuum tank is that a slight variation of this level willaffect the flow from the tank on the paper machine, which fiow must bekept constant, whereas a difference in elevation of the liquid level inthe discharge leg will.

have little or no effect upon this flow. However, if with proper controldevices, a fixed liquid level could be maintained, there would be nodisadvantage in having the level within the tank. Nevertheless, thiswould be affected by the design of the tank. In a tank that is wide andshallow, it is difficult to control the liquid level, whereas a tankthat is narrow and deep might, under good conditions, be operated with aliquid level within the tank. The prime essential is that the flow tothe paper machine is maintained significantly constant.

Further, it is highly important that the suction on the tank bemaintained uniform. The main body portion of the tank should have avolume enough to provide ample space for the upflow of the separated-outair passing to and through the vacuum pump while at the same time notinterfering with the descent of the falling de-aerated or degassifiedwater and fibers. The vacuum preferred lies in a range of fromsubstantially 14 or 15 inches of mercury upward. The length of the legused on the tank has a relation to the degree of suction used (if thede-aerated stock is removed from the leg by gravity) in that the legshould be long enough so that it has as minimal requirements, one footof length for each inch of mercury of the vacuum used. However, if thede-aerated or degassified stock is removed from the leg by means of asuction pump, then the leg needs to be long enough only to collect thede-aerated stock under the following conditions:

The leg, when it has a gravity discharge, must be long enough (1) tominimize air-leakage through it into the tank, and (2) to providesufilcient hydraulic head of stock to cause the stock to fiow from theleg to the paper-making machine against any resistance that it mayencounter in so doing. The leg, when it has a pump discharge, must havea volumetric or detention capacity sufiicient to provide the dischargewith an ample reservoir of stock from which to pump, for its rates ofdischarge must be substantially constant, yet the quantity of stockaccumulated in the leg must not have its liquid level reachsignificantly into the main body of the tank wherein the sprayed stockis being vacuum treated, since, if the main body of the tank is toosmall to permit the sucked-out air to be removed from the tanksubstantially as rapidly as it is so removed, the efficiency of thismethod of treatment falls rapidly. So the hydraulic head exerted by thede-aerated stock in the leg should be fairly constant in order to meetthe requisite of uniform feed of the de-aerated stock to the papermachine, but ordinarily since the vacuum used is uniform and constant,the discharge of stock from the leg can be equally uniform and constant.

The invention is illustrated in the accompanying drawings wherein isshown the best embodiment of this invention now known to me, but it isto be understood that the embodiment is chosen for illustrative purposesonly, and is not limiting, for obviously changes of details and ofconstruction can be made so long as they fall within the ambit of theappended claims.

In the drawings, Fig. l is an isometric view of one embodiment of myinvention, shown more or less diagrammatically and with parts insection. Fig. 1 is an associated apparatus to which conditioned stock issupplied from the apparatus of Fig. 1 but this figure is drawn on a muchsmaller scale than Fig. 1 Fig. 2 is an isometric side elevation of mypreferred form of spray nozzle, while Fig. 3 is a top plan view thereof,with parts in section. Fig. 4. is a vertical elevational view throughone form of vacuum tank of this invention, and Fig. 5 is across-sectional view thereof on the line 55 of Fig. 4.

The vacuum de-aerating tank of this invention shown at H, has a mainbody portion [2, a top i3 which is preferably domed, a coned bottomsection It and a depending leg l5 having certain requirements as tolength and volumetric capacity. Suction is applied to the tank throughpipe or conduit !6 leading to a vacuum pump 11 or other vacuum-producingmeans such as a steam jet. Since it is important to assure constant anduniform suction on the tank, there is provided some suction controlmeans [8, such as a vacuum. breaker illustrated by Way of example as apipe is terminating'in a valve seat 20 having a coned valve 2| adaptedto seat on it and be held thereon by means of its stem 22 on whichadjustable removable and replaceable Weights 23 are provided. 24indicates a suitably located pressure gauge or other device forindicating the degree of suction being applied to the tank II.

The tank is fed with stock to be treated from a source of constantsupply, shown symbolically at 25, pumped by pump 26 through pipe orconduit 21 leading into the upper part of the tank H, where itterminates in a spray nozzle 28 of special construction. Conditioned andde-aerated stock accumulated in the leg l5 to a liquid level such as 29(below the tank) is led (as shown by the arrows at its end) whileminimizing airleakage into the leg, to a stock-treating apparatus shownby example in Fig. 1''. The apparatus illustrated diagrammatically at 30is a cylinder mold and vat, although a head-box for a paper-makingmachine can be substituted for it, if so desired.

The preferred construction of the spray nozzle 28 is shown in Figs. 2and 3. It has a cylindrical body portion 3|, a coned top 32, a conedbottom 33 terminating in a depending orificed neck or spout portion 34.The nozzle has a feed portion or section 35 communicating from a flange38 to the interior of the nozzle in a tangential manner. This feedportion tapers in cross section from the flange 36 to the point 0 whereit joins the body portion 3| of the nozzle 28. It will be noticed thatthis type of nozzle has no interior obstructions of any kind and itbreaks up the liquid fed to it by swirling centrifugal action and emitsthe liquid in the form of a very The operation of this embodiment is asfollows: The dilute paper stock for feeding to the vacuum tank isaccumulated in the box 25 so that it provides a constant source ofsupply. It is sucked therefrom by the pump 26 which pumps the stock tothe tank and the nozzle 28 wherein the stock is broken up into a veryfine spray that is emitted from the orificed neck or spout portion 34 ofthe nozzle. The suction within the tank is equal to at leastsubstantially inches of mercury due to the action of the vacuum pump llsince it is controlled by the vacuum breaker is. If suction becomesgreater than that for which the vacuum breaker is set, the valve 2! issucked off its seat in spite of the weights 23 that tend to hold it onits seat. Upon being unseated, the suction is broken by the inrushing ofair through the seat 20 in pipe IS. The Weights 23 are adjustable orvariable so the vacuum breaker can be made adjustable to give anydesired response.

Stock emitted from the neck 34 of the nozzle 2 8 is de-aerated both ofits entrained and its dissolved air. The reason is that completede-aeration or degassification is a surface phenomenon. And since thestock is atomized into a very fine spray, a maximum amount of surface isexposed to the suction, and de-aeration results in a minimum of time.The ole-aerated air tends to eddy and to rise to be sucked out throughpipe l6 and out through the vacuum pump II. The de-aerated stock fallsdown through the tank which is completely smooth so that there isnothing to which the falling de-aerated stock can ad here. The stock, inmore or less fluid condition accumulates in the leg IE to form a pool ofstock therein whose liquid level 29 is controlled so that even though itmay fluctuate slightly, it is always below the main body l2 of the tank,due to the volumetric capacity of the leg, and preferably even below theconed bottom 14. The importance of this is to assure that there is amplespace in the tank to permit the escape of the de-aerated air or gas forthere should be enough space so that the escaping air does not tend toset up an increased pressure in the tank. De-aerated stock flows bygravity from the leg I5 to further treatment such as in the cylindermold vat of Fig. l or a paper machine. This delivery of the deaeratedstock, while de-aerated, directly to the place where it is to be madeinto paper, prevents re-entrainment or readsorption of a fresh or newsupply of air. Since the stock is completely conditioned by beingde-aerated of both entrained and dissolved air, there is no tendency tofoam or to fiocculate, which renders such stock amenable which fibers ofthe stock can lodge and thus clog the nozzle.

Proportionate and relative dimensions are important in the functioningof embodiments of this invention, as has been previously indicated. Byway of example, it may be stated that the following has been foundsatisfactory: Main body of tank l2, four feet in diameter and three feethigh; the leg I5 is fifteen feet high and twelve inches in diameter; thepipe 2! is six inches in diameter, while the pipe I6 is four inches indiameter; a suction equal to fifteen inches of mercury; the height ofthe spray nozzle is approxi mately six inches; its length about thirteeninches; and its orifice three inches. In this tank, one spray nozzle canhandle from 800 to 1000 gallons of stock per minute, so if a greatervolume is to be treated, more than one spray nozzle can be used in onetank and a larger tank used.

In the practice of this invention, it has been found that thepaper-making fibers so treated, are free from occluded, adhering oradsorbed air or gas and the wateris free from dissolved air, and thefibers no longer have any attraction for each other. Indeed, they seemto repel each other and thus form a definite dispersion in their aqueousmedium or carrier whereupon they settle rapidly since they reassumetheir true specific gravity. Such fibers do not form a ,fiocculent massin the head-box of the paper machine or as they pass along on themachine wire. They settle readily and rapidly and quickly form a mat onthe wire, retaining more of the fine fibers and filling material than innormal current practice.

The embodiment shown in Figures 4 and 5,

differs from the embodiment of Fig. 1 in that inthe latter, itsde-aerated stock flows from the leg I5 by gravity; in the presentembodiment such stock is flowed from the leg by means of a suction pump.In Figs. 4 and 5, M indicates the de-aerating enclosed tank having amain portion or section 32, a domed top 33, a tapered or conical bottomportion or section it, and a leg A5, leading to a suction discharge pump46, which, in turn, is connected to and delivers into the headbox of apaper machine, shown generally in Fig. l The domed top 13, if largeenough, may have a manhole and cover 48 and a suction in dieator 49.Suction from a suction or vacuumproducing pump (such as I! in Fig. loperates through pipe or conduit 59 leading to the interior of the tankii. Diluted paper-mill stock, from a source of supply, such as tank 25,is pumped by pump such as (both in Figure 1 through pipe or conduit 51leading to a bustle-pipe 52 that preferably encircles the tank 4| andfeeds stock to a plurality of spray nozzles 53, 5Q, 55 and 55, forexample, each of which corresponds to nozzle 28 and is substantiallyrepresented by Figs. 2 and 3.

The leg includes a coupling section 51 having a T 58 including a fitting59 that is provided with a wire cloth screen held between rubbergaskets, for a purpose hereinafter described. This T 58 leads through apipe 6! which conneets with the bustle pipe 52. Pipe 6| is provided witha water inlet pipe 52 leading from a suitable supply of water, andvalves 63 and 64 are included in pipe 6! for control purposes. T 58 alsoleads to a pipe 65 connected with the interior of the tank H through itstop 33, which pipe is equipped with sections such as 55, 67 or 68, anyor all of which may comprise suitable gauge glasses by which the liquidlevel in the tank may be observed. H3 represents brackets by which thetank may be suitably supported in an elevated position.

The operation of the embodiment of Figs. 5 and i is as follows: dilutepaper-mill stock is pumped continually through feed pipe 5! so it flowsinto the bustle pipe 52 and thence is forced through the plurality ofspray nozzles 53, 54, 55 and 56 (each substantially like spray nozzle 23of Figs. 2 and 3, or their equivalent). Meanwhile the vacuum-producingpump causes suction to 0perate in th tank il through suction pipe 50.

The result is that the dilute stock emitted in spray form from thenozzles into the smooth interior of the tank ll on which the vacuum issucking, becomes de-aerated (as in tank ll of Fig. 1 and, falls downinto leg 45, where it is collected and accumulates to provide a constantsupply of de-aerated stock to be pumped by the suction pump 46 andforced to the paper machine head-box. Since a pump sucks the de-aeratedstock from the leg, it is not necessary to hold therein as muchhydraulic head as it is when the stock is discharged from the leg bygravity as in Fig. l However, it is still important that the main bodyportion 42 of the tank be kept free of the liquid level of anyaccumulated de-aerated stock, but the operator can be sure of this byobserving the gauge glasses 68, 81 or 66, as the case may be. Fibersfrom the stock do not get into the pipe 65 or its gauge glass sectionsbecause of the screen provided in the fitting 5s to prevent flow offibers therethrough. However, sometimes fibers will clog the screen onthe coupling section side, but in such an event, they can be back-washedby opening the valve 63 in pipe 6| to allow wash water from pipe 52 tofiow back through the screen and coupling 5'! into the dilute stock inthe leg 45. Water from pipe 62 may also be used to back-wash thebustle-pipe 52 and its associated spray nozzles, by opening valve 64 inpipe 6| that connects with the bustlepipe.

The degree of suction used in this embodiment should meet therequirements as hereinbefore described, and this also applies to theliquid level of the de-aerated stock in the leg. It is likewiseimportant to maintain a sufiicient column or body of de-a'era-ted stockin the leg so that there is an accumulation of such stock for the pump46 to draw upon because the feed of de-aerated stock to the paper-makingmachine must be significantly uniform.

A vacuum tank 8 feet in diameter with four nozzle and having a capacityof 250 cubic feet has been found to have sufficient capacity to handle3,000 gallons of dilute paper stock in one minute, and a tank 4 feet indiameter with a capacity of 50 cubic feet with one nozzle was capable oftreating 800 gallons per minute.

While it is believed that the foregoing contains all of the informationneeded by one skilled in the art to practice this invention, therelative importance of some of the feature specified may be betterappraised by the following explanation of what is believed to be thetheory of the functioning of the invention:

As has been stated, it is the object of this invention to remove fromthe fibers that are in water-suspension in the paper-making stock sothat as they go onto the paper machine, they are sufficiently de-aeratedthat they are not flocculent; are not scum-forming; are not buoyant;have substantially no occluded air; and tend to sink when submerged. Inorder to accomplish this, they must be substantially removed or isolatedfrom being in suspension in water. The reason for this is that theeffect of the vacuum to which they are subjected, is significantly towithdraw or suck air from the fibers while they are in water-suspensionbecause the vacuum cannot reach through the water to the fibers. It isknown that vacuum is ineffective to reach down into a body of waterbeyond or beneath its liquid level. Therefore, if the fibers are encasedin a substantial body of water, the vacuum cannot penetrate that body tode-aerate the fibers. Accordingly, this invention proposes to force-feedthe stock to an atomizing device or spray nozzle that is located withinthe vacuum-induced zone of reduced pressure within the tank, and thenforcibly to project the stock from that atomiz- 8 ing device into thereduced pressure zone so that the stock is rendered into an atomizedmist of such discrete fine particles that the fibers are substantiallysegregated from the water particles. In other words, the fibers aresufficiently separated from their water carrier that they are in effectchanged into gaseous suspension, and have so little water left on themthat the vacuum can reach them and suck the water from them. or at leastreduce any water on them to a monomolecular film that is incapable ofretaining occluded air in it while under the influence of the vacuum.And when the fibers are relieved of occluded air, they are no longerflocculent, or froth-forming, and indeed they tend to sink whensubmerged. Meanwhile, the water particles have air sucked therefrom bythe suction.

The de-aerated water particles and the deaerated fibers fall into thepool in the bottom of the tank where the de-aerated fibers are againrendered into water-suspension but since the water is also tie-aerated,the resulting condition is such that any tendency of the fibers to bereaerated by air in the water is minimized.

The formation of the discrete particles and the segregation of the waterparticles and the fiber particles are facilitated by the use of the typeof spray nozzles disclosed herein to which the stock is pressure-fedtangentially and wherein, because of the partially cylindrical andpartially conical shape of the nozzle induces swirl of the stock thereinwith the result that cyclonic er centrifugal action is set up whichtends to force the heavier fibers to the outside of the cone and thelighter water to the center thereof. The emission of stock from thenozzle seems to explode the particles into an extremely fine state ofsubdivision.

These advantageous effects are not to be obtained merely by flowing thinfilms of paper making stock over a cone in a vacuum tank, such as isshown in my prior Patent No. 1,853,849. Moreover, paper making stockcannot be treated in ordinary water de-aerating sprays under vacuum tode-aerate the fibers because that type of apparatus does not meet any ofthe requirements carefully set forth herein.

What I claim is:

1'. The method of de-aerating air-bearing fibers in dilute paper-makingstock prior to being supplied to a paper machine, which comprisesestablishing and. maintaining a gaseous body under the effect of vacuumto be at reduced pressure, force-feeding into an atomizing zone suchstock in the form of a dilute water suspension containing such fibers,forceably projecting such suspension from such zone under atomizingconditions that render the suspension into gassuspended discrete fineparticles of water and of fibers in such a state of subdivision that theeffect of the vacuum can reach to the fiber particles to remove airoccluded by those fiber particles and can reach the water particles tosubstantially de-aerate them, collecting such deaerated water particlesand ole-aerated fiber particles in a pool still under the eifect of suchvacuum wherein the de-aerated fibers are resuspended in de-aerated waterin which the fibers sink and remain in substantially air-free condition,and conducting such air-free watersuspension to a paper machine.

2. The method according to claim 1, wherein the suspension is swirlinglyexpelled and projected from the atomizing zone.

3. Apparatus for de-aerating air-bearing fibers in dilute paper-makingstock, which comprises an enclosed tank having a pool receivingandcollecting-portion in the lower section thereof; vacuum producing meansfor establishing and maintaining a reduced pressure within the tank; afeed conduit for conducting the stock of water-suspended fibers to thetank including a manifold and a plurality of cylindrical spray nozzleshaving fiber-swirling coned smooth interiors resistant tofiber-adherence with a tangential feed portion connected to the manifoldand with a depending reduced outlet for forcibly p j cti the stock intothe tank as an atomized spray of discrete finely divided particles; thepool-receiving portion of the tank being so placed with respect to thenozzles that atomized spray from them descends to and is collected inthat pool-receiving portion as a pool of de-aerated fibers suspended inde-aerated water, and means for passing such suspension to a papermachine.

4. Apparatus for de-aerating air-bearing fibers in dilute paper-makingstock, which comprises an enclosed tank having a pool-receiving andcollecting-portion in the lower section thereof; vacuum producing meansfor establishing and maintaining a reduced pressure within the tank; afeed conduit for conducting the stock of water-suspended fibers to thetank, a cylindrical spray nozzle having a smooth interior resistant tofiber-adherence with a tangential feed portion connected with the feedconduit,

and with a depending reduced outlet for forcibly projecting the stockinto the tank as an atomized spray of discrete finely divided particles;the pool-receiving portion of the tank being so placed with respect tosaid nozzle that atomized spray from the same descends to and iscollected in that pool-receiving portion as a pool of daerated fiberssuspended in a de-aerated water, and means for passing such suspensionto a paper machine.

5. Apparatus for de-aerating air-bearing fibers in dilute paper-makingstock, which comprises an enclosed tank having a pool-receiving andcollecting-portion in the lower section thereof; vacuum producing meansfor establishing and maintaining a reduced pressure within the tank; afeed conduit for conducting the stock of Water-suspended fibers to thetank, a spray nozzle comprising a main cylindrical body part with atangential feed inlet portion connected with the feed conduit, and saidspray nozzle having a coned bottom terminating in a depending outlet forforcibly projecting the stock into the tank as an atomized spray ofdiscrete finely divided particles, said spray nozzle having a smoothinterior resistant to fiber adherence; the poolreceiving portion of thetank being so placed with respect to the spray nozzle that atomizedspray from the same descends to and is collected in that pool-receivingportion as a pool of deaerated fibers suspended in de-aerated water, andmeans for passing such suspension to a paper machine.

JUDSON A. DE CEW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,569,105 West Jan. 12, 19261,853,849 De Cew Apr. 12, 1932

